1. Field of the Invention
The present invention relates to an image forming apparatus using electrophotography, such as a copier, a printer, a facsimile apparatus, etc. and a process cartridge to be installed in the image forming apparatus, and in particular relates to a process cartridge unit that can be detachable relative to the main body of an image forming apparatus and an image forming apparatus provided with a mechanism to transmit a driving force to the process cartridge unit.
2. Discussion of the Background
Recently, a process cartridge unit in which process devices, such as, a photoconductor, a charging device, a development device, a cleaning device, etc, are integrated is used in an image forming apparatus in a detachable manner to reduce the size of the apparatus and to facilitate maintenance of the apparatus.
Japanese Patent Laid-open publication No. 8-339153 describes a process cartridge unit including an electrophotographic photoconductor and a developer bearing member. A drum gear is provided to an end part of the photoconductor to engage with a drive gear of the main body of an image forming apparatus, a sleeve gear is provided to an end part of the developer bearing member to engage with the drum gear of the photoconductor, and the sleeve gear of the developer bearing member is engaged with gears of other rotary members (a toner stirring member, etc.) via a gear row.
Thus, in the process cartridge unit described in the above-described JP publication, drive forces for all rotary members in the process cartridge unit are obtained from the side of the main body of the image forming apparatus via the drive force transmission mechanism relative to a single rotary member (i.e., the photoconductor) and are transmitted to the other rotary members via the gear row. Therefore, within the process cartridge unit, the layout of the gear row is restricted by the positional relationship between image forming elements (the photoconductor, the developer bearing member, a charging device, a development device, a cleaning device, etc.), and further, the space occupied by the drive force transmission mechanism within the process cartridge unit is relatively large.